The present invention relates to a cassette door latch and, more particularly, to an improved door latch for latching a tape cassette access door.
In tape cassettes and, more particularly, video tape cassettes, a door is frequently provided on the cassette for covering the tape which is threaded between the reels of the cassette when the cassette is removed from the recording or playback machine. When the cassette is installed in the recording or playback machine, the door is automatically opened to allow contact of the tape which is then exposed with the recording or playback heads of the machine. When the cassette is removed from the machine, the door is automatically closed and latched in the closed position to protect the tape against damage or contamination.
Prior door latching mechanisms for tape cassettes are disclosed, by way of example, in U.S. Pat. No. 4,212,437. The latches disclosed in that Letters Patent all employ a separately installed spring which urges the latching member of the latch into its latching position relative to the door to latch the door in its closed position. Such separately installed springs have several disadvantages. They require increased inventory of parts and the manipulation and installation of both the separate latching member itself and the spring in separate steps. In certain of these prior latches, the spring is extremely tiny. Thus, the spring is difficult to manipulate by hand, and is virtually impossible to install by automated procedures. Moreover, the presence of the multiple, separate pieces results in increased material and installation costs and increases the possibility that the separate pieces may become separated after installation, either in transportation, in use or if the cassette housing is taken apart for any reason after it has been assembled.
In U.S. Pat. No. 4,323,207 a latch and spring is disclosed which overcomes some of the aforementioned disadvantages of the mechanisms which employ separate latching members and springs. That Letters Patent discloses a slidable latch mechanism for latching the door of a tape cassette in the closed position which includes a spring molded integrally with the latch to urge the latch toward its latching position. The integral latching mechanism as disclosed in that Letters Patent has the disadvantage, however, of requiring a substantial force on the mechanism to move it toward its unlatched position. Another disadvantage of this latching mechanism is that it is subject to excessive "creep" which is a condition inherent in plastics which causes them to set in a certain shape after a period of time, particularly when exposed to higher temperatures such as might be encountered in the recording or playback machine. Such "creep" results in the spring taking a set when confined in its unlatched position, thereby reducing the ability of the spring to return the latch to its latched condition. Still another disadvantage of the latching mechanism disclosed in this Letters Patent is that the latching member and its spring are of considerable size and occupy a substantial portion of the already restricted and compact area which is available in the cassette housing.
A latch incorporating the principles of the present invention overcomes these several aforementioned disadvantages. A latch incorporating the principles of the present invention eliminates the need for separate latching members and springs and, thus, reduces the number of parts. Such reduction in the number of parts in the present invention reduces both the material and installation costs, reduces the amount of parts needed to be kept in inventory, and not only facilitates hand assembly of these mechanisms, but also facilitates assembly of these mechanisms by automated procedures. A latch incorporating the principles of the present invention also reduces the likelihood of separation of parts, either in use, in transportation or upon disassembly of the cassette housing. A latch incorporating the principles of the present invention may be readily installed without the need for major redesign of previously configured housings to render the housings compatible to the latch of the invention. A latch incorporating the principles of the present invention is readily operable with a minimum of force and under the environmental conditions normally encountered by tape cassettes and requires only a minimum of space in the cassette housing.
In one principal aspect of the present invention, a latch for the door of a tape cassette comprises a substantially rigid latching member for latching the door closed, mounting means for mounting the latching member for rotation about an axis between latching and unlatching positions, and spring means for urging the latching member toward the latching position. The spring means includes a resilient arm having one end formed in integral, one-piece relationship to the latching member and the arm projects from the latching member in the direction of rotation of the latching member toward the unlatching position.
In another principal aspect of the present invention, the one end of the arm which is attached to the latching member is located between the axis of rotation and the free opposite end of the arm.
In still another principal aspect of the present invention, the one end of the arm which is attached to the latching member is spaced from the axis of rotation and the other free end of the arm is nearer the axis of rotation than to the one end of the arm.
In still another principal aspect of the present invention, in the last mentioned configuration elongate torsion means extends substantially perpendicular to the resilient arm, the torsion means is formed in integral, one-piece relationship to the arm and the latching member and mounts the arm to the latching member for rotation of the arm relative to the latching member about an axis substantially perpendicular to the arm.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description.